1. Field of the Invention
The present invention relates to an electrode substrate for a display device, more specifically, to a structure of an array substrate used in an active matrix liquid crystal display device.
2. Description of the Related Art
In recent years, active matrix liquid crystal display devices are becoming mainstream in the field of flat display devices due to reasons including high contrast with small crosstalk, capability of transmissive display and large-screen display, and the like. A liquid crystal display device known of this type is disclosed in Japanese Unexamined Patent Publication No. 2002-296619.
FIG. 1 is a plan view showing a schematic configuration of a pixel in a conventional liquid crystal display device. Meanwhile, FIG. 2 is a cross-sectional view taken along the I—I—I line in FIG. 1, and FIG. 3 is a cross-sectional view taken along the II—II line in FIG. 1.
The liquid crystal display device includes an array substrate 100 and a counter substrate 200 which are disposed to face each other, while a liquid crystal layer 300 is formed in a space between the both substrates.
The array substrate 100 includes scan lines 102, auxiliary capacitor lines 130 disposed in planarly parallel to the scan lines 102 on the same plane, and signal lines 101 disposed in planarly perpendicular to the scan lines 102 and the auxiliary capacitor lines 130 through an insulating film 160, all of which are formed on a glass substrate 105.
A pixel TFT 110 is formed at an intersection of the signal line 101 and the scan line 102 as a pixel switching element. A protection film 170 is formed on a surface of this pixel TFT 110. Moreover, a color filter 180 and a pixel electrode 120 are formed in a region surrounded by the signal lines 101 and the auxiliary capacitor lines 130 (the region indicated by bold lines in FIG. 1). The pixel TFT 110 includes a semiconductor layer 111, a gate electrode 112 connected to the scan line 102, a drain electrode 113 connected to the signal line 101, and a source electrode 114 connected to the pixel electrode 120.
Here, reference numeral 140 in FIG. 2 denotes an outgoing line connecting the drain electrode 113 of the pixel TFT 110 and the pixel electrode 120, reference numeral 150 denotes a gate insulating film, and reference numeral 190 denotes an alignment film formed on a surface of the pixel electrode 120. A polarizing plate 195 is attached to outside of the glass substrate 105.
The counter substrate 200 includes a counter electrode 210 and an alignment film 230 which are sequentially formed on a glass substrate 220. Moreover, a polarizing plate 240 is attached to outside of the glass substrate 220.
As shown in FIG. 2 and FIG. 3, the signal line 101 for supplying a video signal and the drain electrode 113 of the pixel TFT 110 are connected to each other through a contact hole 115 which is provided so as to penetrate the insulating film 160 and the gate insulating film 150. Conventionally, the contact hole 115 has been disposed between adjacent pixel electrodes 120, and respective ends of the adjacent pixel electrodes 120 have been separated by a constant dimension at aperture portions of the contact hole 115.
However, in the array substrate 100 of the above-described configuration, a horizontal dimension A from a bottom of the contact hole 115 to the end of the pixel electrode 120 may become shorter than a horizontal dimension B of a tapered portion of the contact hole 115 because of manufacturing errors when forming the pixel electrode. In this case, an electrode material such as ITO tends to remain at recessed portions of the contact hole 115 indicated by arrows in FIG. 3 when forming the pixel electrodes 120. Accordingly, there has been a risk of a short circuit between the adjacent pixel electrodes 120 attributable to the remaining electrode material. When the adjacent pixel electrodes 120 are short-circuited as described above, the pixels turn out to be defective pixels because of incapability of retaining original write voltages. Accordingly, such a short circuit would constitute a problem of reduction in yields.
An object of the present invention is to provide an electrode substrate for a display device which can achieve fabrication of liquid crystal display devices at high yields by reducing short circuits between adjacent pixel electrodes.